Steels capable of withstanding the high temperatures commonly utilized in various industrial processes, such as the pyrolysis of various hydrocarbon materials, are well known. A problem common to a number of such processes is that of the formation of "coke", a carbon-rich material which forms deposits on the surfaces defining the reaction zone and in downstream quench equipment. Coke represents a substantial deficit in operations, since it restricts flow and is a thermal insulator. Thus, as coke deposits on the reactor surfaces, higher and higher tube wall temperatures are required to sustain the reaction or process in operation.
A common practice conducted in such operations is known as "de-coking". To carry out de-coking, process operations are periodically discontinued and the deposits are removed by various techniques, e.g., by oxidation with a steam/air mixture. The required downtime results in substantial loss of operation or production, and much effort has been expended in attempts to extend the time between de-coking.
Evidence exists that nickel and iron in the steels used for reactors promote coking in certain temperature ranges. A variety of techniques have been employed to overcome the presence of the nickel and iron, with varying results. Accordingly, a technique or equipment which might extend the time before de-coking is required and/or inhibit coking so that the process operations might be carried out at greater severities would have great economic value. Also, a pyrolysis process having these characteristics would be of great importance. The invention is directed to such.